1. Field of the Invention
The present invention relates to an automatic focusing or focus control device for use in a camera with which exchangeable objective lenses are selectively and detachably mounted, and more particularly it pertains to a coupling mechanism between a focus control mechanism in the camera and a lens driving mechanism in the exchangeable objective.
2. Description of Prior Art
An automatic focusing device for an objective lens exchangeable camera has been proposed by a Japanese Laid-Open Patent No. 48-53718. In the known device, however, an objective lens is axially displaced by a lens mount which supports an objective lens and is moved along the optical axis of the objective. Because of its arrangement, such device is applicable only to a specific type of objective in which focusing is made by the entire lens system being integrally moved. In addition, it is difficult for such device to avoid increases of its weight and size because the lens mount and a bearing or support for it must be made large and steady in order to displace a comparatively heavy objective in a predetermined incremental displacement range (which is generally large in may interchangeable lenses) without tilting the optical axis of the objective.
Further difficulties may be encountered when such an automatic focus device is to be associated with an objective which, as is common with single lens reflex cameras, has a so-called automatic diaphragm aperture control device wherein, in response to a shutter release operation, the diaphragm is stopped down to an aperture value manually preset or an aperture value to be automatically determined in accordance with scene brightness. For example, a coupling pin interlocking a diaphragm mechanism in the objective with a camera mechanism has to be made long enough to maintain the interconnection even when an objective mount is displaced fowardmost to a hyperfocal position. On the other hand, the coupling pin must not interfer with any mechansim inside the camera, e,g, a reflex mirror for a single-lens reflex camera when the objective is displaced rearmost to an infinity (focused position). Thus, the known mechanism imposes great restrictions on the mechanisms incorporated in a camera or provided between the camera and the objective, and restricts the variety of combinations between camera bodys and exchangeable lenses.